Neuropathic pain reducing agent and antidepressant agent, each using neuropeptide

[Problem] To develop an agent that satisfies the treatment of neuropathic pain. Namely, to develop an excellent neuropathic pain reducing agent for mammals, which has few side effects. [Solution] A neuropathic pain reducing agent for mammals or an antidepressant agent for mammals, which is characterized by containing a peptide represented by the following formula (1) as an active ingredient. x-y-Gly-Trp-NH 2 (1) (In the formula, x and y each represents zero or one amino acid selected from among Pro, Gly, Ala, Val, Leu, Ile, Met, Phe and Trp.) Consequently, a low-cost neuropathic pain reducing agent for mammals having few side effects is able to be provided. Since these peptides increase the amount of brain serotonin, these peptides can be provided as antidepressant agents for mammals.